-2x2+8x=4

Solution for -2x2+8x=4 equation:

-2x^2+8x=4

We move all terms to the left:

-2x^2+8x-(4)=0

a = -2; b = 8; c = -4;
Δ = b2-4ac
Δ = 82-4·(-2)·(-4)
Δ = 32
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{32}=\sqrt{16*2}=\sqrt{16}*\sqrt{2}=4\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4\sqrt{2}}{2*-2}=\frac{-8-4\sqrt{2}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4\sqrt{2}}{2*-2}=\frac{-8+4\sqrt{2}}{-4}
$